______,Bring water to the boil in the bottom of a metal steamer.,Put the peas in a steamer rack.,Place the rack over the boiling water, cover and steam the peas until tender, about 10 minutes (depending on the size and the age of the peas).,If frozen peas are used, simply put them in a sieve and pour boiling water over them briefly.,Put the peas in a saucepan.,Meanwhile, combine the mustard, vinegar, pepper and salt in a mixing bowl and blend well.,Heat the oil in a skillet and add the mustard sauce.,Rinse out the small mixing bowl with the water and add it.,Cook, stirring, about three or four minutes and add it to the peas.,Stir to blend.